At present, Ba—W dispenser cathodes composed of the barium calcium aluminates are being used as the cathodes in microwave vacuum electron source devices for various civil and military uses. The development of high frequency and high power microwave devices speeds the requirement for cathodes that can provide high emission current density. However, Ba—W dispenser cathode could not provide enough emission current density to meet such requirement. As a promising and optimal candidate cathode, scandate cathode has shown superior emission property at lower operation temperature over Ba-dispenser cathode, and it could be taken as the future of the thermionic cathodes.
In all kinds of scandate cathodes, lots of attention have been paid to the pressed scandate cathode having such an advantage over the impregnated scandate cathode as its simple preparation process, for example, the cathode could be obtained after high temperature sintering whereas three-step high temperature treatments of high temperature sintering, impregnating at high temperature followed by annealing in hydrogen are indispensable for the preparation of impregnated scandate cathode. However, the pressed scandate cathode has lower emission property than the impregnated cathode, which could be attributed to the non-uniform distribution of various active substances in the cathode and micrometer dimension of matrix structure usually used in the ordinary cathodes. If the sub-micron structure matrix preparation technique and liquid phase doping technology are applied to the manufacturing of the pressed scandate cathode, it is expected to improve the emission performance of this cathode, and thus the said emitter will be the ideal cathode for the microwave vacuum device due to its good emission property and the simple and reproducible preparation process.